<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const url = 'http://localhost:3000'
        const data = {
            username: '格格'
        }
        const myHeaders = new Headers({
            'X-Costom-Header': 'NJY'
        })
        fetch(url,{
            method: 'POST',
            body: JSON.stringify(data)
        })
        .then(res => res.json())
        .then(res => {
            console.log(JSON.parse(res.postData));
        })
    </script>
</body>
</html>